Estee, that is awful that you've felt like you can't take time off when you're sick, and as you alluded to, I think that in itself is a stress that can exacerbate illness.

And going into work when you're experiencing depression and/or anxiety, well, all I can say is I admire you tremendously and
I'm on the other end of the spectrum - I take too many days off sick. For me it's an issue of either I take a day or two to come to grips with the depression or I have to quit altogether. (Which I've done in the past) So, taking time off for me is the better choice.
I'm praying for the time when I don't battle as much with this illness and can be relatively "symptom-free."